1. Field of the Invention
This invention relates to shrouds for the recovery of fuel elements in a nuclear power plant.
2. Discussion of Related Art
In a nuclear power plant the life of a fuel element is limited to a few years only. This life expectancy is further shortened if a defect of any kind is found to affect a single component of the fuel element. Each element comprises a large number of components in the form of rods and damage to one of these rods leads to the removal of the entire assembly from service. The rods consist of pellets contained in a tight metal can. These rods are placed in bundles in a structure with a square cross section which structure consists of two vertically spaced plates joined to each other by means of a series of mounting tubes. Grids, which are perforated by holes, are threaded on the mounting tubes in a regularly spaced manner. These grids serve to hold the rods in position. The upper plate serves as the raising system for the fuel elements. The lower plate is equipped with four feet placed at the corners and acts as the bearing surface of the fuel element on the bottom of the pool. When it is found that one rod in a fuel element is damaged, the defective fuel element is withdrawn to remove it from service.
However, over a certain period of time, for economic reasons, a method has been developed for the recovery of rods remaining intact in defective fuel elements. This method requires a series of manipulations involving a high degree of risk that the broken or damaged rods will become detached from the fuel element and will drop into the pool, thereby contaminating the latter.
To eliminate these disadvantages, the defective fuel element is placed in a shroud which retains all of the debris. To utilize the raising system initially provided for the fuel element, the shroud must be attached to the structure of the fuel element itself.